Encryption & Decryption using native PowerShell Convert functions

Encrypt-Decrypt-WithConvert.ps1

## Encryption & Decryption via ConvertFrom-SecureString and ConvertTo-SecureString

## This is Symetrical encryption. Which means the same key is used to both encrypt and decrypt.

## The encryption method is based on AES 256bit.


$KeyFile = 'c:\temp\AWS.key'
$EncFile = 'c:\temp\AWS.aes'
$DecFile = 'c:\temp\AWS.json'


##### Create Sample Text
$Text = [pscustomobject] @{
    TypeName = 'AWS.Account'
    Access   = '..xxx'
    Secret   = '..yyy'
    Region   = 'eu-west-1'
    Account  = '..111'
} | ConvertTo-Json
$Text | Out-File $DecFile


##### Generate a password
$Bytes = [byte[]]::new(1024)
[Security.Cryptography.RNGCryptoServiceProvider]::Create().GetBytes($Bytes)
$SpecialChars = @(40,41,33,64,36,37,45,61,46,63,42,59,38) 
$Filter = {
    ($_ -ge 97 -and $_ -le 122) -or  # a - z
    ($_ -ge 65 -and $_ -le 90)  -or  # A - Z
    ($_ -ge 50 -and $_ -le 57)  -or  # 2 - 9
    ($SpecialChars -contains $_)     # ()!@$%-=.?*;&
}
$text  = [Text.Encoding]::ASCII.GetString(($Bytes | where $Filter))
$pass  = $text.Substring(0,128)


# create a key by hashing the password 
$algo  = [System.Security.Cryptography.HashAlgorithm]::Create('SHA256')
$bytes = [System.Text.Encoding]::ASCII.GetBytes($pass)
$StrB  = [System.Text.StringBuilder]::new()
$algo.ComputeHash($bytes) | foreach {[void]$StrB.Append($_.ToString('x2'))}
$Key   = $StrB.ToString(0,32) | Out-File $KeyFile -Encoding utf8 -NoNewline


##### Encrypt the File
$key    = [byte[]][char[]](Get-Content $KeyFile -Raw)
$Text   = Get-Content $DecFile -Raw
$SecStr = ConvertTo-SecureString -String $Text -AsPlainText -Force
$EncStr = $SecStr | ConvertFrom-SecureString -Key $Key  # <-- encryption
$EncStr | Out-File $EncFile -Encoding utf8 -NoNewline


##### Decrypt the File
$key    = [byte[]][char[]](Get-Content $KeyFile -Raw -Encoding UTF8)
$EncStr = Get-Content $EncFile -Raw -Encoding UTF8
$SecStr = $EncStr | ConvertTo-SecureString -Key $Key    # <-- decryption
$BinStr = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($SecStr)
$Text   = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BinStr)
$Text | ConvertFrom-Json


# the Encryption is done via: ConvertFrom-SecureString
# the Decryption is done via: ConvertTo-SecureString